But … wait … put down those frikadeller (meatballs in Danish). As chef Trine Hahnemann explains, many unwritten rules need to be followed to create an authentic version of the food that has been part of her country’s culture since the Middle Ages.

The butter must be salted. Each sandwich should have three of the five basic tastes — salty, sweet, sour, bitter and umami. Always include something soft and something crunchy. Never combine fish and meat. Eight Houstonians standing around a tall table full of farm-fresh heirloom tomatoes, eggs and herbs listen closely as Hahnemann explains a few of the rules — and when they can be broken. Then, under the celebrity chef’s guidance, they start crafting their sandwiches — slicing eggs, snipping dill and slathering on tarragon mayonnaise, horseradish cream and other handmade condiments from their host’s kitchen.

Book signing

Hahnemann’s enthusiasm for these aspiring smørrebrød masters is surprising since she’s already spent a 12-hour day at her job as an ambassador for modern Nordic food. Author of 16 cookbooks, including the best-selling “Scandinavian Baking,” she oversees a catering service that provides fresh, organic lunches for 3,000 employees at public and private companies in Copenhagen. She travels often as an advocate for sustainable practices, and she co-founded the Rye Bread Project in New York, which donates heritage rye seeds to U.S. agricultural interests in an attempt to reintroduce the grain in this country.

This year she opened Hahnemanns Køkken, a bakery, coffee bar, food store and cooking school in north Copenhagen. In May, she published “Open Sandwiches” and this month released “Copenhagen Food.” Part cookbook, part city guide, part personal reminiscence, her latest effort, she says, is an attempt to capture what daily life is like in the city she’s called home for 50 years.

“It’s more than a memoir; it’s how I see the world through food,” says Hahnemann, who will appear Saturday at River Oaks Bookstore.

Rye bread and herring: Ten years ago, that’s what anyone not living in Scandinavia (along with many who were) would have imagined when they thought about Nordic cuisine — if they thought about it at all. But in 2010, the Copenhagen restaurant Noma was named the best in the world, and the city quickly evolved into a cosmopolitan food destination, much like Houston has in recent years.

A multistarred Michelin restaurant with sea-snail broth as a starter and plankton mousse cake as dessert isn’t for everyone’s taste, or budget. But Noma was a game changer as the city embraced “New Nordic” cuisine, with its emphasis on local sources, seasonal menus and the innovation of traditional dishes. As Noma chefs left the mother ship to open their own restaurants, Copenhagen residents learned to appreciate sustainable, farm-to-table cuisine.

Chapters in “Copenhagen Food” are organized by neighborhood. Their names, “Nyhavn,” “Gammelholm” and “Nørrebro,” may be a mouthful for English speakers — but the recipes are accessible.

“I created a lot of the recipes so you can get a little dream of what it’s like in Copenhagen,” Hahnemann says. She emphasizes easy-to-find ingredients, and not too many of them. Since the city is surrounded by water, for example, seafood is plentiful. But, she adds, “If you cook at home, you probably don’t have fish stock.”

Tradition reigns in Denmark; herring, aquavit, rye bread, even hot dogs remain essential in the Danish diet. But Hahnemann modernizes the classics, such as Hakkebøf with hasselback potatoes. Chanterelle mushrooms instead of gravy flavor the patties, and the potatoes are roasted, not boiled. Cod with hollandaise is accompanied with sautéed kale and chewy beets.

Salads represent modern Danish cooking, so Hahnemann has included more than a dozen among the 70 recipes in her new book. She also stresses fresh ingredients. Though Scandinavian countries are known for their long, dark winters, Hahnemann frames her year in terms of food.

“We really have 10 seasons here in Denmark. Strawberries are available for four weeks, asparagus, six weeks. We grow things month to month, and after the season is over, you don’t see that food anymore.”

“Copenhagen Food” may be a cookbook, but it is a personal one. “It is not a general guide book, it’s my history of my city,” Hahnemann writes in the introduction. “This is the way I live in Copenhagen.”

She shares stories about growing up in Nyhavn, where Hans Christian Andersen wrote some of his fairy tales, and the street dinner party she and her Østerbro neighbors hold each year.

She describes her favorite walks and bicycle rides, and recommends sights to see, places to eat and stores to hit. Photographs infused with gentle Scandinavian light illustrate the city and its residents.

“I’d like people to know that Copenhagen is really easy to visit and to get around,” she says. Hahnemann is also a fan of Houston; she lists the city’s museums, Central Market, The Breakfast Klub and T’afia, Monica Pope’s now closed farm-to-table restaurant, as highlights of her most recent trip eight years ago.

“It’s a place I could imagine living,” she says — high praise from someone whose home is regularly named “the happiest country in the world.”

Smørrebrod assembled, the Houstonians follow Hahnemann to a large wooden table below two crystal chandeliers. Though the chef has now been working for 14 hours, she pours wine, opens beers and sits down to discuss Danish food culture for a little longer in a display of what the Danish call “hygge,” a hard-to-translate concept of coziness and camaraderie.

The new masters — impressed with their delicious results — start debating where in Houston they can find herring, dense rye and soft fresh cheese worthy of Danish smørrebrod.

Roberta MacInnis is the Houston Chronicle's Arts Editor and writes Running Notebook. She was born in Fairbanks, Alaska, and graduated from the University of Alaska with a degree in journalism. She has been running more than 30 years, is a member of the Houston Marathon Veterans, and has twice qualified for the Boston Marathon.